Antagonists of the receptor-G protein interface block Gi-coupled signal transduction.

Gilchrist A, Mazzoni MR, Dineen B, Dice A, Linden J, Proctor WR, Lupica CR, Dunwiddie TV, Hamm HE
J Biol Chem. 1998 273 (24): 14912-9

PMID: 9614095 · DOI:10.1074/jbc.273.24.14912

The carboxyl terminus of heterotrimeric G protein alpha subunits plays an important role in receptor interaction. We demonstrate that peptides corresponding to the last 11 residues of Galphai1/2 or Galphao1 impair agonist binding to A1 adenosine receptors, whereas Galphas or Galphat peptides have no effect. Previously, by using a combinatorial library we identified a series of Galphat peptide analogs that bind rhodopsin with high affinity (Martin, E. L., Rens-Domiano, S., Schatz, P. J., and Hamm, H. E. (1996) J. Biol. Chem. 271, 361-366). Native Galphai1/2 peptide as well as several analogs were tested for their ability to modulate agonist binding or antagonist-agonist competition using cells overexpressing human A1 adenosine receptors. Three peptide analogs decreased the Ki, suggesting that they disrupt the high affinity receptor-G protein interaction and stabilize an intermediate affinity state. To study the ability of the peptides to compete with endogenous Galphai proteins and block signal transduction in a native setting, we measured activation of G protein-coupled K+ channels through A1 adenosine or gamma-aminobutyric acid, type B, receptors in hippocampal CA1 pyramidal neurons. Native Galphai1/2, peptide, and certain analog peptides inhibited receptor-mediated K+ channel gating, dependent on which receptor was activated. This differential perturbation of receptor-G protein interaction suggests that receptors that act on the same G protein can be selectively disrupted.

MeSH Terms (18)

Adenosine Animals Baclofen Binding, Competitive Brain Cells, Cultured Electrophysiology GTP-Binding Proteins Humans Male Peptide Fragments Rats Rats, Sprague-Dawley Receptors, GABA Receptors, Purinergic P1 Rhodopsin Signal Transduction Xanthines

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